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Power Sanding Finish?


j. pierce
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I hate hand sanding. I've gotten skilled enough with hand planes that I can avoid the majority of it, and where that doesn't work, cabinet scrapers come in handy. But all that is moot when it comes to the finish. I'm annoyed by it, and it never even occurred to me that I can use power tools in that application. The particular bit that's bugging me is leveling the epoxy grain-fill I put on under the KTM-9 finish I use, but I wouldn't mind getting away from going by hand when I wetsand the finish before buffing and polishing.

Is this an application where a palm sander would work well? Can I wet sand with a palm sander? Do I need a particular type of palm sander? I assume if liquid is involved, I probably want to use air powered, and not electric tools - but maybe this is just a no go in general? Anything I should look for out there when I'm poking around for these things? I know next to nothing about power-sanding solutions, Is micromesh available for palm sanders?

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Yeah, that was my fear.

I have used a pad sander for scuff sanding cabinet parts at work before and I just saw in martin koch's guitar making book a company that used an air one for scuff sanding. I'm not sure if they used wet or dry, I used dry and went over the surface once twice if it needed it no more. You would have to be careful but to do the back and the front it's possible.

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Abralon sells orbital sanding discs in 180-4000 grit. They can be used wet or dry. I haven't used them personally, but I don't see why they wouldn't work for the flat surfaces. The orbital is actually pretty controllable. I use it with 220 or 320 sometimes for flat sanding after grain filling. Erikbojerik has said he uses Abralon, and the finish on his last project was about 10 feet deep. Don't know if he uses a power sander, though.

Another way to save some sanding is to get your finish to level out really good while you're spraying. When I used conversion varnish, the finish leveled so well that I could sand a guitar completely flat by hand with 1000 grit paper in about 45 minutes.

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i use a makita 1/4 sheet palm sander

in benedetto's book he recomends using a 1/4 sheet palm sander

just make sure you don't move too quick, be thorough, use fresh paper and use every grade grit you can get

beyond 1500 you need to be using cutting compound

oh make sure you have a good solid thickness of well cured lacquer

also you will still needa do the edges by hand :D

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I level with a randomly-orbital (electric!) sander using 320-400-600 dry when it comes to levelling a grain fill. I make sure everything is nice and smooth at the 600-grit stage before applying finish - prep sanding is the first key to a great finish. To avoid sanding hard on the edge, make sure the spin of your orbit has the sandpaper sliding OFF the edge rather than into the edge, just pay attention to which way it's spinning and where you are on the instrument.

Build coats I usually end up levelling with 600-grit wet (soapy water) by hand with a hard rubber or wood block - my random-orbital is a velcro job and I just don't feel like the velcro system has a hard-enough backing to get the finish as level as I want. To me there is no avoiding this step.

At the buff-out stage (after levelling with 600-grit) I use Abralon 1000-2000-4000 foam pads wet, with the random-orbital - but I'll also use them by hand in tight spaces. Then 3M Fine Cut followed by Meguiar's Swirl Remover on separate StewMac foam pads chucked into an electric drill which is held in a vise, so that I can hold the instrument with 2 hands. Also paying attention to having the pad spin OFF the edges rather than into them.

A great finish always requires a certain amount of work by hand IME.

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